The Chemical Pharmaceutical Bulletin 21, 457 (1973) discloses a method in which desmosterol acetate was epoxidated with m-chloroperbenzoic acid to form 3.beta.-aotoxycholest-5-ene-24,25-epoxide, which was then reacted with sulfuric acid to prepare 24,25-dihydroxycholesterol-3-acetate, or a method in which 24,25-dihydroxycholesterol-3-acetate was obtained by reacting desmosterolacetate with osmiam oxide. The above 24,25-dihydroxycholesterol-3-acetate was converted to 24,25-dihydroxycholecalciferol by a conventional method.
This method has a drawback that it involves a number of processing steps for preparing desmoterolacetate which is used as a raw material; in addition, in the former of the method the yield of 24,25-dihydroxycholesterol derived from desmosterolacetate is low. In the latter of method, osmium oxide used as reagent is expensive and toxic.
Therefore, the above mentioned method was not commercially advantageous.
On the other hand, the Biochemistry 12, 4851 (1973) discloses that 24,25-dihydroxycholecalaferol was obtained from 3.beta.-hydroxy-27-norcholest-5-ene-25-one-3-acetate. This method has a drawback that it involves a great number of processing steps.
1.alpha.,24,25-trihydroxycholecalciferol has previously been synthesised by almost same method as mentioned above.